This invention relates to a rear wheel supporting device for a vehicle, such as a motorcycle, having a cantilever swing arm, and, more particularly, to a rear wheel supporting device for a motorcycle having a partition structure provided between the brake disc and the sprocket arranged close to opposite sides, respectively, of the rear free end of the swing arm, so as to physically separate the brake disc and the sprocket thereby to protect the surface of the brake disc. The partition structure also contains a baffle arrangement adapted to effectively discharge lubricating oil splashed by the rotating sprocket outwardly of the vehicle body.
It is known to use a cantilever swing arm as a rear wheel supporting device for a motorcycle. Such swing arms are adapted to be pivotably mounted at one end on a rear portion of the vehicle body frame and to contain at the other end, which is its free end, a vehicle axle supporting portion on one side of which the rear wheel of the vehicle is provided. Since such a type of swing arm makes it possible to attach and detach the rear wheel at one side of the vehicle body, it is more advantageous from the vehicle maintenance standpoint and has been received favorably, particularly in the field of racing vehicles, or the like.
In the case of cantilever swing arms of the described type, since the brake disc and the sprocket are provided at opposite sides of the vehicle axle supporting portion, they are arranged relatively close to each other as compared with their being arranged on a fork like member of the prior art. For this reason, the surface of the brake disc may be damaged by fine, granular metal pieces, or other debris, developed from impacting of the chain with grains, for example, sand grains spattered by rotation of the sprocket. Accordingly, one aspect of the present invention is intended to prevent scattering of such grains thereby to protect the surface of the brake disc.
Also, in a chain-drive type motorcycle, where it is ordinary to arrange a chain case along the chain, the chain case has a sectionally inverted-U-shape so as to cover the chain. By this structure, the oil which may be splashed by the chain and sprocket is prevented from further splashing outwardly from the vehicle.
In such structures, however, oil splashed by rotation of the chain and sprocket, generally adheres to the top inside of the chain case, then is driven downwardly by the wind which occurs during driving and/or by vibration. Therefore, if the chain case is disposed above a cantilever swing arm, the surface thereof is easily and widely contaminated by receiving the fallen oil droplets. Furthermore, it is difficult to remove the spots resulting from the oil droplets within the interior region of the vehicle body. Therefore, it is another object of the present invention to provide means capable of removing such splashed oil efficiently from the motorcycle body.